wl1271: Implement CMD_SET_STA_STATE to indicate connection completion to FW

Implement the command function to send CMD_SET_STA_STATE to the firmware. This
is used to indicate that association (and the related EAP negotiation) are
complete.

This is used to tune WLAN-BT coexistense priority towards BT, improving BT
A2DP and SCO performance.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Teemu Paasikivi <ext-teemu.3.paasikivi@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>